Microsoft Office Communicator Web Access (2007 R2 release) is an extension of Office Communications Server 2007 R2. It is not a stand-alone application. You cannot install Communicator Web Access unless you have already installed Office Communications Server 2007 R2 within your Active Directory forest. In addition to needing Office Communications Server 2007 R2, there are hardware and software requirements for both Communicator Web Access servers and clients, as described in Walkthrough: Hardware and Software Requirements. For additional details about the prerequisites for deploying Communicator Web Access, see Verifying Communicator Web Access Requirementsin the Deploying Communicator Web Access (2007 R2 Release) documentation.